How to Fix Your Organization Used Windows Defender Application Control to Block This App

If your organization has enabled Windows Defender Application Control (WDAC), it can sometimes block legitimate applications from running, causing disruptions to your workflow. This guide will walk you through the process of lifting or modifying WDAC policies to unblock specific applications. Before starting, ensure you have administrative privileges on your device and access to group policies or the local security policy editor, depending on your organization’s setup. Making changes to WDAC policies can impact your system’s security, so proceed carefully and consider consulting your IT department if you’re in a managed environment.

What You’ll Need

• Administrative access to your Windows device
• Knowledge of the specific app you want to unblock (executable path or hash)
• Access to Group Policy Editor or local security policies (if applicable)
• Optional: Windows PowerShell with administrative privileges

Step-by-Step

1. Identify the Blocked Application
   • Attempt to run the app. If Windows Defender Application Control blocks it, you will typically see a notification or an event log entry.
   • Check the Event Viewer: Press Win + R, type “eventvwr.msc”, and press Enter.
   • Navigate to Windows Logs > Security or Application, and look for events related to WDAC or AppLocker indicating the app was blocked.
2. Gather Application Details
   • Locate the application’s executable file (.exe).
   • Right-click the app, select Properties, and note the path.
   • For added security, you can generate a hash (SHA-256): open PowerShell as admin and run:

     Get-FileHash "C:\Path\To\YourApp.exe" -Algorithm SHA256

   • Record the hash value for later use.
3. Open the Group Policy Editor or Local Security Policy
   • Press Win + R, type “gpedit.msc” to open the Group Policy Editor (if available).
   • If your environment uses Local Security Policies, type “secpol.msc” instead.
4. Create or Edit the WDAC Policy
   • Navigate to Computer Configuration > Administrative Templates > System > Device Guard > Application Control Policies.
   • If using PowerShell, you can create custom WDAC policies using the Windows Defender Application Control tools.
     • Open PowerShell as administrator.
     • Use the `New-CIPolicy` cmdlet to generate a policy that allows the specific app.
     • Example:

       New-CIPolicy -FilePath "C:\Path\To\YourApp.exe" -Level Publisher -UserPEs -FileHash

     • Save the policy as a .cip file.
     • Sign the policy with your organization’s signing certificate.
     • Import the policy using `Set-CIPolicy` or the appropriate management tool.
5. Deploy the Updated Policy
   • Import the new or modified WDAC policy into your system.
     • If using PowerShell, run:

       Set-CIPolicy -FilePath "C:\Path\To\Policy.cip"

     • Or, via Group Policy, import the policy through the Administrative Templates or security settings.
   • Restart your computer or refresh policies to apply changes.
6. Verify the App Runs Properly
   • Attempt to launch the application again.
   • Check Event Viewer to confirm it is no longer blocked.
   • Ensure the app functions as expected.

Common Mistakes

• Not verifying the exact application or hash before modifying policies, leading to unintentional security risks.
• Editing policies without proper backups, making it difficult to revert changes if something goes wrong.
• Assuming that disabling WDAC entirely is necessary, instead of creating exceptions for specific apps.
• Neglecting to sign custom policies, which can cause them to be rejected by Windows.
• Applying changes without restarting or refreshing policies, resulting in the old policies still being enforced.

Tips

• Always create a backup of your current WDAC policy before making modifications.
• Use the `Get-CIPolicy` command to export current policies for review.
• Test changes on a non-production system first to prevent widespread issues.
• Coordinate with your IT department if you’re in a managed environment to ensure compliance.
• Use PowerShell scripts for automation if you frequently need to unblock applications.
• Keep documentation of all changes made to policies for auditing purposes.

Troubleshooting

If the application still does not run after modifying WDAC policies, consider the following steps:

• Revisit the Event Viewer to check for new block events or errors related to the app.
• Ensure the policy has been correctly imported and applied. You can verify current policies with PowerShell commands like `Get-CIPolicy`.
• Check if there are other security measures, such as AppLocker or third-party security software, blocking the app.
• Make sure the app’s executable path or hash matches exactly what is specified in your policy.
• Reboot your system after applying policy changes to ensure they take effect.
• If issues persist, revert to the previous policy backup and seek assistance from your IT support team.

Frequently Asked Questions

1. Can I disable Windows Defender Application Control entirely?

Yes, but it is not recommended as it reduces your system’s security. Instead, consider creating exceptions for specific apps.

2. How do I know if an app is blocked by WDAC?

You can check the Event Viewer for block events or attempt to run the app; if blocked, you’ll receive a notification or error message.

3. Is it safe to modify WDAC policies?

Modifying WDAC policies can expose your system to risks if not done carefully. Always back up policies and verify changes before deployment.

4. What is the difference between WDAC and AppLocker?

WDAC uses code integrity policies to control application execution at a kernel level, while AppLocker manages application rules at a higher level, often easier for administrators to configure.

5. Can I undo changes if I accidentally block a critical app?

Yes, always keep backups of your policies. You can revert to a previous version or delete specific rules to unblock apps.

6. How often should I review WDAC policies?

Regular reviews are recommended, especially after system updates or changes in the application environment, to ensure security and functionality.

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